1. Field of the Invention
A magnetic resonance imaging apparatus is an apparatus which images the chemical and physical microscopic information of a substance or observes a chemical shift spectrum by using a phenomenon in which when a group of nuclei having a unique magnetic moment is placed in a uniform static field, they resonantly absorb the energy of a radio-frequency magnetic field that rotates at a specific frequency.
2. Description of the Related Art
In diagnosis of ischemic heart disease, as a method of evaluating myocardial hemodynamics using a magnetic resonance imaging apparatus, there is available a method (myocardial perfusion) of observing the process of imaging the cardiac muscle with a contrast medium by injecting the contrast medium through a vein and performing left ventricular short-axis multislice contrast-enhanced T1-weighted imaging together with an ECG-gated technique during the first circulation. The result obtained by this myocardial perfusion is evaluated by continuously displaying (cine-displaying) the respective slices in the time direction or by dividing each left ventricular short-axis slice into a plurality of radial regions, converting various measurement values obtained from graphs (dynamic curves) representing temporal changes in signal values in the respective divided regions into developed views, i.e., so-called Bull's eye images, in which the measurement values are concentrically arranged from the cardiac base to the cardiac apex in correspondence with a color map or gray scale, and displaying the image, as described in, for example, Sakuma et al., “Diagnosis of Ischemic Heart Disease by Contrast Medium MRI”, INNERVISION (15.13) 2000, pp. 59-66, Nanjou et al., “Myocardial Perfusion/Evaluation of Cardiac Muscle Viability”, INNERVISION (17.9) 2002, pp. 10-14, and Fujimoto et al., “Points of Anatomical/Physiological Function Necessary for MRI in Cardiovascular Region”, INNERVISION (17.9) 2002, pp. 1-4.
In order to obtain an electrocardiographic waveform, it takes a lot of trouble to attach electrodes for electrocardiographic signal detection to a subject to be examined before examination. In addition, depending on patients, in order to obtain a proper electrocardiographic signal, it takes much time to, for example, re-position the electrodes. Furthermore, noise caused by gradient field switching for magnetic resonance imaging may be induced into an electrocardiographic waveform. As a result, proper synchronization may not be established, and imaging operation cannot be performed or image quality may deteriorate.
In addition, since a radio-frequency pulse for magnetic resonance imaging is applied while the electrodes are attached to the subject, the radio-frequency pulse is induced into the loop formed by the electrodes, a wire for transferring an electrocardiographic waveform, and the human body. This may cause a burn. This risk increases in high magnetic field MRI with high radio-frequency pulse power.
In addition, since conventional moving image display is performed for each slice, it is difficult to observe the state of blood supply in the entire cardiac muscle at a glance.